In recent years, with the increase in capacities in hard disks in computer equipment, the densities for recording information in a single recording layer are increasing. For example, in order to increase the recording capacity for each unit area of a magnetic disk, the areal density must be increased. However, as the areal density increases, the recording area occupied by each one bit decreases on a recording medium. In a decreased bit size, the energy that information of one bit has becomes closer to thermal energy at ambient temperature, which causes a problem of heat demagnetization including that recorded information thereon may be inverted or be lost due to heat fluctuation, for example.
The longitudinal magnetic recording, which has been used in general, is a method for recording magnetism such that the direction of magnetization can be the longitudinal direction of a recording medium. In this method, the loss of recorded information may be easily caused by the heat demagnetization. Accordingly, in order to solve the problem, a shift is on its way to perpendicular recording that records a magnetization signal in a perpendicular direction to a recording medium. This method is a method that records magnetization information on a recording medium on the principle that a magnetic monopole is brought close thereto. With this method, the recorded magnetic field points substantially in the perpendicular direction to a recording film. The information recorded with a perpendicular magnetic field can easily keep the stability in energy because producing a loop by the N-pole and the S-pole is difficult within a recording layer. Therefore, the perpendicular recording is more resistant to heat demagnetization than longitudinal recording.
However, recent recording media have been demanded further increases in density in response to the need for recording/reproduction of a large amount of information at a high density, for example. For that reason, highly coercive recording media have been started to be adopted in order to minimize the influences between adjacent magnetic domains and/or the heat fluctuation. Therefore, it has become difficult even for the perpendicular recording to record information on recording media.
Accordingly, in order to solve the problem, hybrid magnetic recording has been proposed that locally heats a magnetic domain with near-field light to reduce the coercivity temporarily and performs writing thereon during the period. The hybrid magnetic recording is a method that uses near-field light generated by the interaction between an infinitesimal area and an optical aperture in a size equal to or smaller than the wavelength of the light formed in a near-field optical head. In this way, by using a near-field optical head having a minute optical aperture beyond the diffraction limit of light, that is, a near-field light emitting device, optical information in an area equal to or smaller than the wavelength of light, which has been considered as the limit with conventional optical systems, can be handled. This may facilitate the increase in density of recording bits beyond conventional optical information recording/reproducing apparatus and so on.
Notably, the near-field light emitting device may have a projection in a nanometer size, for example, instead of the optical minute aperture. Also with the projection, near-field light can be generated as from the optical minute aperture.
As one of proposed various information recording/reproducing apparatus based on the hybrid magnetic recording, an information recording/reproducing apparatus is known (Publication 1 of unexamined application: International Publication WO 00/28536) that generates a sufficiently large quantity of near-field light from a minute aperture by supplying light for generating near-field light to a near-field optical head, whereby ultrahigh-resolution reproduction/recording, high-speed recording/reproduction and a high SN ratio can be sought.
The information recording/reproducing apparatus includes, as shown in FIG. 13, a gimbal 30 provided at a pointed end of an arm, not shown, a first substrate 31 fixed to the gimbal 30 rotatably about an X-axis and a Y-axis, a second substrate 32 fixed to the bottom surface of the first substrate 31, and a third substrate 33 fixed to the bottom surface of the second substrate 32.
The first substrate 31 has a V-groove, and an optical waveguide 34 that guides laser light L into the V-groove is placed therefor. The laser light L emitted from the tip of the optical waveguide 34 is configured to be reflected by an optical reflective layer 35 on the first substrate 31 and enter to the second substrate 32.
The second substrate 32 has a lens 36 that condenses the laser light L reflected by the optical reflective layer 35 to a minute aperture 39, which will be described later, of the third substrate 33. The third substrate 33 has a tapered through-hole 38 on which a light reflective film 37 is deposited, and the center of the through-hole 38 is the minute aperture 39. Then, near-field light S is generated by the laser light L condensed to the minute aperture 39. The bottom surface of the third substrate 33 has a slider surface (ABS: Air Bearing Surface) 33a facing a rotating disk D and is designed to levitate by receiving the air flow with the rotation of the disk D.
A slider 40 is composed of the second substrate 32 and third substrate 33.
In a case where information is to be written on the disk D by the information recording/reproducing apparatus having the configuration above, the arm is moved to scan by a voice coil motor, for example, after the disk D is rotated first, and then the slider 40 is moved to a desired position on the disk D. At that time, the slider 40 has a state that it is levitating at a predetermined height from the disk D because it receives the levitation force by the third substrate 33. Because the slider 40 is fixed to the arm through the gimbal 30, it can rotate about an X-axis and a Y-axis in connection with the undulation of the disk D that is rotating at a high speed, and the levitating attitude can be stable. Thus, the distance between the minute aperture 39 and the disk D can be kept constant.
Next, the laser light L is launched to the optical waveguide 34. The launched laser light L propagates within the optical waveguide 34 and is guided to the tip. The laser light L emitted from the tip of the optical waveguide 34 is reflected by the optical reflective layer 35 and then enters to the second substrate 32. The laser light L incident on the second substrate 32 is condensed by the lens 36 and is guided to the minute aperture 39. Thus, the near-field light S occurs near the minute aperture 39. The disk D is locally heated by the near-field light S, and the coercivity decreases temporarily. As a result, information can be written on the disk D.
Publication 1: International Publication WO 00/28536